An electrical accumulator battery is subject to two ageing processes:                cycling: the cycles of charging and discharging cause the battery to deteriorate;        over time: prolonged storage of the battery results in corrosion reactions damaging the battery over time.        
The ageing of a battery manifests as a decrease in its capacity and an increase in its internal resistance.
A state of health (SOH), defined as a ratio of the storage capacity of a battery at a time t to the capacity of the battery at the start of life, characterizes the ageing of the battery. In general, a state of health of 80% is considered to be characteristic of a battery at the end of life. A battery considered to be at the end of life has therefore lost 20% of its capacity and its internal resistance has increased, by about 30% for a lithium-ion battery.
Thus, a battery having for example a capacity of 96 A.h at the start
of life has a capacity of only 77 A.h at the end of life.
Nowadays, the batteries installed on board aircraft with all-electric propulsion have a service life of about one year. The relatively rapid deterioration of these batteries constitutes an operational drawback, since the energy capacity of the battery decreases over time, reducing their autonomy.
One envisageable solution to this problem is to use batteries having a longer service life. One drawback of this solution is the very high cost of this type of battery.
U.S. Patent Application US 2016/0167541 describes a method for monitoring the electrical controls of a vehicle. A torque to be applied to the vehicle depends on a position of the accelerator pedal. There is a risk that the current imposed on the batteries is higher than necessary, if the accelerator pedal is depressed beyond the required position, causing the battery to age prematurely. The method described in the U.S. patent application manages the temperature of the battery by virtue of a cooling system and limits the torque to be applied if this torque could bring about damage to the battery.
However, although this method slows the ageing of the battery, it does not
make it possible to maintain a substantially constant level of energy performance independently of its state of health.
French patent FR3002045 describes a method for managing the charge of a battery according to which the maximum permissible state of charge of the battery is limited, which limit increases as the battery ages, so as to anticipate the decrease in the energy capacity of the battery and to maintain a constant available energy level over the service life of the battery.
One drawback of this method is that it does not take the discharge level into account, i.e., the battery undergoes premature ageing in the event of an overly deep discharge.